The present invention relates to a fluid circuit arrangement which is used for temperature control purposes.
The fluid circuit arrangement may be used in any environment where temperature control is required; such control is to involve not only control of the temperature of the fluid with in the circuit arrangement itself, but of a second fluid passing in, through over or around a heat exchange means of the circuit arrangement.
It should be appreciated that the first fluid and the second fluid may be the same or different but it is particularly envisaged that the first fluid will be a liquid such as water and the second fluid will be a gas specifically air.
Although various uses for the fluid circuit arrangement are envisaged, the invention is particularly applicable in the context of cooling/heating circuits for use in association with prime movers such as diesel engines, internal combustion (i.e.) engines, gas turbines, etc. where the first fluid is water flowing in the circuit arrangement and the second fluid is air which is to be utilised in the combustion process.
To take the specific example of a large horsepower diesel engine the fluid circuit arrangement comprises the main engine temperature control system and includes a heat exchange means which is commonly referred to as a jacket, cooler or radiator whereby heat is removed from the engine to its surroundings. A high power diesel engine will inevitably involve a turbocharging arrangement which involves the introduction into the combustion cylinders via the inlet manifold of air under pressure (charge air) from a compressor. As the air is compressed by the compressor of the turbocharger its temperature is raised. The benefit of the high pressure is substantially reduced if the charge air temperature is allowed to remain at this high temperature and, accordingly, the usual arrangement is to provide a cooling means between the compressor and the inlet manifold. Such cooling means, which is generally referred to as an intercooler or charge air cooler, will involve a heat exchange arrangement through which water is passed to take heat from the charge air passing therethrough, or therearound.
In full load conditions, air leaving the compressor can be at a temperature which may be as high as say 210xc2x0 C., which temperature is drastically reduced to say 70xc2x0 C. as the charge of air passes through the intercooler.
It is known to interconnect the circuit for cooling water for the intercooler and the main engine or jacket cooling circuit via a valve arrangement whereby heat from the intercooler circuit may be dissipated via the heat exchange means of the main jacket circuit and heat from both circuits may be dissipated via a cooling means in the intercooler circuit.
However, the known arrangements mean that under certain conditions, e.g., where the engine is first started, too much heat is lost from the system when it would be more efficient to maintain the temperature at a value higher than ambient temperature.
The present invention seeks to provide a fluid circuit arrangement where the requisite temperature control can be achieved under various operating conditions.
According to the invention there is provided a fluid circuit arrangement comprising a first fluid circuit and a second fluid circuit, an interconnecting means which connects the first circuit and the second circuit, the first circuit and the second circuit having a first fluid for circulation therein, the first circuit comprising a first heat exchange means adapted to exchange heat between the first circuit and its surroundings, the second circuit comprising a cooling means for controlled cooling of the first fluid and a second heat exchange means adapted for the exchange of heat between the second circuit and a second fluid, the second circuit also comprising a valve device which is actuable by a control means responsive to at least the temperature in the first circuit to control the flow of first fluid through the cooling means, and at least one of the first circuit and the second circuit comprising a heating means for heating of the first fluid.
It is preferably arranged that during said controlled cooling, said first fluid circulating in both the first circuit and the second circuit passes through the cooling means.
Both the first circuit and the second circuit may comprise respective said heating means.
The heating means may comprise respective electric heaters provided with respective thermostats.
The control means may also be responsive to the temperature of the second fluid passing through the second heat exchange means.
Preferably the valve device comprises two inlet ports and an outlet port and a valve element movable under control by the control means to progressively close one inlet port as the other inlet port is progressively opened; as the one inlet port is progressively closed and the other inlet port is progressively opened, the first fluid is caused to flow through the cooling means.
The control means may progressively actuate the valve device in response to respective ranges of temperatures in the first circuit or in the second heat exchange means.
The first fluid circulating in the first and second circuits is preferably a liquid.
The interconnecting means may comprise a temperature responsive valve device which operates to interconnect the two circuits at a predetermined temperature and the temperature responsive valve device may be operated progressively to connect the first circuit to the second circuit as the temperature in the first circuit increases over a range of temperatures.
A fluid circuit arrangement as defined above may be combined with a diesel engine. In such a combination the first heat exchange means may comprise a jacket cooling means and the second heat exchange means may comprise an intercooler between a compressor and an inlet manifold of the engine. In a standby condition of the engine, the heating means may operate whereby the temperature of the first fluid in the first circuit is maintained at or above a first predetermined temperature and the temperature of the first fluid in the second circuit is maintained at or above a second predetemined temperature; the second predetermined temperature is higher than the first predetermined temperature, and the control means may be responsive to the temperature in the intercooler and/or the pressure of air in the intercooler and/or the speed of the engine. Further the control means may respond to increasing load of the engine to operate the valve device progressively to bring the cooling means into the circuit whereby the fluid flowing through the second circuit is cooled via the cooling means. Further, the control means may respond to low and/or decreasing load of the engine to operate the valve device progressively to take the cooling means out of circuit.
An embodiment of the invention is shown by way of example in the accompanying drawings.